The reputation of Julio Cesar Chavez Jr. precedes him. That’s not a good thing, either.

He has never had the fire of his famous father. He twice has been suspended by the Nevada State Athletic Commission for post-fight positive tests for marijuana and the diuretic Furosemide, respectively. Perhaps most importantly, he hates to train.

It’s that latter knock that Chavez is going to try and erase in one fell swoop with his performance Saturday against Canelo Alvarez. The two Mexicans will square off at a sold-out T-Mobile Arena in Las Vegas (on HBO pay-per-view).

Chavez, 31, has always been seen as someone who could have gotten more out of his career had he been more dedicated. As it is, he’s only lost twice and has a draw and a no-decision in 54 fights, and he is a former middleweight champion.

Losing his middleweight title to Sergio Martinez in September 2012 was one thing. Retiring after nine rounds against Andrzej Fonfara in April 2015 at StubHub Center was quite another.

But Chavez seemed to make a good move when he hired famed Mexican trainer Nacho Beristain to train him for this fight. By all accounts – including camp photos circulated by his conditioning trainer Memo Heredia – Chavez is apparently training harder than ever.

“The difference is I was listening to my corner,” Chavez said this week via conference call. “Mr. Beristain, he had me doing certain training and I did it. It was very difficult in the beginning getting used to this new regimen, but it’s something that I did.”

Chavez speaks like he takes responsibility for his past misgivings.

“The difference is that I was younger, less experienced,” he said. “And over the years, I’ve learned from those kind of mistakes and the inexperience that I had. And that’s the difference between then and this fight.”

Chavez has to make a catch-weight of 164 1/2 pounds for this bout. If he has worked to make weight the right way – instead of cutting pounds at the last minute like fighters who don’t like to train – that could make all the difference in the world for Chavez because he’ll feel strong rather than drained.

Abel Sanchez trains middleweight champion Gennady Golovkin. If Alvarez beats Chavez, Team Golovkin will be looking to make a deal to fight Alvarez in a long-awaited bout in September.

But Sanchez agrees that if Chavez didn’t come into fight week having to lose eight to 10 pounds, he could give Alvarez a run for his money.

“I think that Canelo wins, but I think he (Chavez) scares Canelo a couple of times, maybe drops him once,” said Sanchez, who said Golovkin would happily fight Chavez if he wins. “But I think that Canelo’s youth, combination punching and speed – not so much foot speed, but just flashy combinations – will give Julio trouble.”

Sanchez said that he, too, has heard Chavez (50-2-1, 32 KOs) is training very hard. As Chavez should be. If he wins this fight, it would be his most significant victory, one that would surely strengthen his legacy.

“Yes, I do feel this is the biggest fight of my career, just because it’s a big event, because of who I’m fighting and because of the opportunity,” Chavez said. “I’m going to take advantage of it and make the best of it.”

That’s not to mention that country pride is on the table, and when it comes to boxing in Mexico, that is serious business.

“It’s very, very important for both fighters,” Chavez said. “Yes, it’s very important for him, but the fact that it’s two Mexicans, I think that this is one of the most important fights in the history of Mexico.”

Moreover, Chavez would rather lose to anyone but Alvarez (48-1-1, 34 KOs). Not only does Chavez want bragging rights in Mexico, the two fighters have grown to dislike each other.

“As a person, I don’t know him well, but just from what I hear from his actions and all, it’s like a guy that just doesn’t sustain what he says,” Alvarez said of Chavez. “You know, he just says a lot of things. It’s almost like he’s a little kid.”

Those are fighting words.

“Yes, there is a real, true rivalry,” Chavez said.

Indeed, if there was ever a fight Chavez was going to really be in shape for, it’s this one. But that doesn’t worry Alvarez one bit.

“On the contrary, I’m very happy that he’s working hard, that he’s training hard and that he’s doing good,” Alvarez said. “Because you know what? That guarantees the people a great fight.”